Multi-stage manual transmissions for motor vehicles, with the exceptions of automatic transmissions in planetary design and double clutch transmissions, are typically designed as simple countershaft transmissions with two axis-parallel transmission shafts that can be selectively brought into drive connection with each other via a plurality of gear sets of different transmission ratios. The gear sets each comprise at least one fixed gear disposed rotationally fixed on one of the two transmission shafts, and one idler gear rotationally supported on the other transmission shaft. For the forward gears, the respective idler gear is in direct gear engagement with the assigned fixed gear, and can be connected rotationally fixed to the respective transmission shaft by means of an assigned gear coupling. For the reverse gear, the idler gear is in drive connection, via an intermediate gear, to the assigned fixed gear for reversing the direction of rotation. By engaging the respective gear coupling, the idler gear of the respective gear set is connected rotationally fixed to the assigned transmission shaft, and therefore the respective gear is engaged within the transmission. By disengaging the gear coupling, the rotationally fixed connection of the idler gear to the assigned transmission shaft is disengaged, and therefore the respective gear is disengaged within the transmission. The gear couplings are typically designed as lock synchronized or unsynchronized dog clutches that each can be engaged or disengaged via a shift collar disposed in a rotationally fixed and axially displaceable manner on the respective transmission shaft.
For actuating the shift collar, and thus for engaging and disengaging a gear within the transmission, a shift rod is typically disposed axis-parallel to the respective transmission shaft and supported in an axially displaceable manner, and is in form locking engagement with the shift collar via a rigidly fastened shift fork that engages in an outer annular groove of the shift collar. Alternatively, the shift rod can also be connected, via a form locking engagement, to a swivel shift lever, that is arranged between the shift rod and the shift collar, and is mounted so that it can be pivoted about a tangential axis of rotation, and engages with a fork-shaped part into the external annular groove of the shift collar.
To limit the constructive space, the idler gears of two adjacent gear sets are each preferably disposed on the same transmission shaft, and the respective two gear clutches are combined in a shift packet with a common shift collar, so that the engaging and disengaging of the respective two gears occurs via an axial displacement of a single shift rod in the respective opposite direction.
In particular with manually shiftable motor vehicle transmissions, the gear sets of subsequent gears are typically arranged on the transmission shafts in axially adjacent pairs, having the same paired association of fixed gears and idler gears to the transmission shafts, and having a common shift packet, so that in each case two subsequent gears can be engaged and disengaged via a common shift rod. Thus, the assignment of the gears to the shift rods corresponds to the typical H or multiple H shift pattern with a plurality of shift gates and a selector gate of a shifting device operated manually by the driver, connecting the shift gates, via which the driver can carry out the selection of the shift gate and the engagement and disengagement of a gear associated with the selected shift gate.
The assignment of the gears in the transmission to the shift rods in this case corresponds to the assignment of the respective gears to the shift gates in the shifting pattern of the manual shift lever. This makes it possible to have a relatively simple mechanical transfer of the selection and shift movements of the manual shift lever via a linkage or cable device outside the transmission and a gear shift shaft inside the transmission, to the shift rods and the shift packets of the transmission, where the gear shift shaft is in most cases disposed vertically to the transmission shafts supporting the gears, and is mounted axially displaceable and rotatable about its longitudinal axis. Through axial displacement of a gear shift shaft disposed in this manner, an assigned shift finger of the gear shift shaft is brought into engagement with a catch of one of the plurality of shift rods, which corresponds to a selection process, that is, the selection of a shift gate. Through rotation of the gear shift shaft about its longitudinal axis, the respective shift rod is axially displaced through the pivoting movement of the shift finger, which corresponds to a shifting process, that is, the engagement and disengagement of a gear of the respective shift gate.
Thus, selection movement of the manual shift lever, that is, a change of the shift lever position between two shift gates within the selector gate, corresponds inside the transmission to a change of the connection for adjusting the gear shift shaft between two shift rods, and shifting movement of the shift lever, that is, a change of the shift lever position between a shift position of a first gear, a neutral position and a shift position of a second gear within the selected shift gate, corresponds inside the transmission to axial displacement of the shift collar that is coupled to the gear shift shaft via the associated shift rod, between a first shift position in which the clutch of the first associated gear is engaged, a neutral position in which the clutches of both associated gears are disengaged, and a second shift position in which the clutch of the second associated gear is engaged.
Manually shiftable transmissions of motor vehicles up to now have typically comprised five or six forward gears, and consequently a relatively small number of shift gates. Known shift patterns of such transmission are shown in FIGS. 5a and 5b. The known shift pattern 20 of a five-speed transmission, according to FIG. 5a, comprises only three shift gates 21, 22, 23, and a selector gate 24 connecting the shift gates. The first gear G1 and the second gear G2 are associated with a first outer shift gate 21. The third gear G3 and the fourth gear G4 are associated with a center second shift gate 22, in which the manual shift lever 25 is held by spring elements within the selector gate 24, and into which the manual shift lever 25 is automatically returned when it is released within the selector gate 24. The fifth gear G5 and the reverse gear R are associated with a third outer shift gate 23.
In order to prevent inadvertent engagement of the reverse gear R, with a shifting device with such a shift pattern 20, typically there is shift interlock that can be designed as a push lock, a push-down lock or as a pull ring lock.
The known shifting pattern 30 of a six-speed transmission, according to FIG. 5b, comprises four shift gates 31, 32, 33, 34 and the selector gate 35 connecting the shift gates. In this shifting pattern 30, in addition to the fifth gear G5, the sixth gear G6 is also assigned to the outer third shift gate 33. The fourth shift gate 34 is disposed outside of the outer first shift gate 31, and allocated only to the reverse gear R.
Accidental engagement of the reverse gear R during a shift procedure with a pattern such as shift pattern 30 can be prevented by a shift interlock of the type described above, and also by a selector interlock, by means of which, starting from a neutral position of the first shift gate 31, selecting the fourth shift gate 34 is made difficult due to an increased selection force, or is prevented by a releasable form fitting lock. Such shift or selection interlocks typically operate together with the manual shift lever 36 in the shift device external to the transmission, and in most cases are vehicle-specific, and limited to use with manual transmissions.
Due to the demands for increasingly lower motor vehicle fuel consumption, an increased number of gears is necessary for the manual transmission because a reduction in the transmission ratio steps between the gears enables nearly constant operation of the respective combustion engine in a rotational speed range with a specific low fuel consumption. This inevitably leads to a higher number of shift gates, which particularly in the case of manual transmissions can lead to an incorrect selection and a shift into an unsuitable gear due to relatively small spacing of the shift gates in the shift pattern of the manual shift lever 47.
To highlight this problem, FIG. 5c shows the shift pattern 40 of an eight-speed transmission having five shift gates 41, 42, 43, 44, 45 and one selector gate 46 connecting the shift gates. This shift pattern 40 that is known in a similar form, expanded by a creep gear, from the shifting device of the commercial vehicle transmission described in DE 39 34 733 A1, in comparison to the shift pattern 30 of the six-speed transmission according to FIG. 5b, comprises another shift gate 44 that is disposed outside of the third shift gate 43, and comprises the seventh gear G7 and the eighth gear G8.
In the case of a manual transmission or a shifting device having such a shift pattern, there is the danger that with an upshift from a gear G3 or G4 of the second shift gate 42 into a gear G5 or G6 of the third shift gate 43, the gate for the gears G5, G6 is unintentionally bypassed and as a consequence a gear G7, G8 of the fourth shift gate 44 is erroneously engaged. This shifting error leads to an increased loss of tractive power and requires an immediate corrective shift into a lower gear G5, G6.
Whereas the delimitation of the reverse gear R, or the shift gate 45 of the reverse gear R, by a shift or selector interlock of the type described above is possible, such a delimitation of the outer shift gate 44 allocated to the forward gears G7, G8 is judged to be unacceptable due to the associated shift delay. Therefore, it appears expedient to equip a shifting device of a multi-stage manual transmission having such a shift pattern with a selector interlock for preventing a selection of the outer shift gate 44 depending on the operation.
A shifting device of a manual transmission having a suitable selector interlock disposed in the transmission for this purpose is described in the document DE 100 31 754 A1. This selector interlock that operates by increasing the actuating force, comprises a spring-loaded ball that is guided perpendicular to the gear shift shaft of the shifting device and is in contact with the surface of the gear shift shaft. Due to an increase in the diameter of the gear shift shaft between an outer shift gate preferably allocated to the reverse gear R and the next inner shift gate, an axial selector movement of gear shift shaft into the outer shift gate results in an increase of the required actuating force, which in the case of an electric motor design of the selector can be recognized by an increased current consumption of an actuator for this regard.
The document, DE 31 41 271 C2, discloses a shifting device of a group transmission having a main transmission and a two-stage range group, that are manually shiftable using a common gear shift shaft that comprises a similar selector interlock of a spring-loaded plunger, which is guided perpendicular to the gear shift shaft and in contact with the surface of the gear shift shaft. The increase of the diameter of the gear shift shaft between a shift gate allocated to the lower gears of the fast speed range and a shift gate allocated to the high gears of the slow speed range, results in an increase of the necessary actuating force for an axial selector movement of the gear shift shaft to the downshift range. Due to the connection of a pressure means, pressure acting, via a pressure piston, on the pressure spring of the plunger, which occurs when exceeding a higher driving speed, the necessary actuating force is increased so that an inadvertent shift into the downshift range is largely excluded.
In contrast, document DE 30 46 885 C2 describes a shifting device of a group transmission having a manually shiftable main transmission and automatically shiftable two-stage range group. The range group is shifted via a double acting shifting cylinder, actuated by pressure means, that is controlled via two directional valves sensing the control contour of a locking body fastened on the gear shift shaft. A locking cylinder aligned perpendicular to the gear shift shaft, that has a locking bolt and can also be controlled by the two directional valves, ensures that the shift gates of the main transmission allocated to the low gears are not selected in the case of a range downshift. In the case of a range downshift, the locking bolt is pressed by the supply of pressure means against the force of a reset spring into a locking position in which axial displacement of the gear shift shaft from the shift gate allocated to the high gears into the shift gate of the main transmission allocated to the low gears is blocked in a form locking manner. After switching the locking cylinder to become pressureless upon reaching the shift gate allocated to the high gears, the pressure medium escapes via a throttle so that the blocking release of the shift gate allocated to the low gears is time delayed.
A shifting device of a manual transmission comprising a similar selector interlock is known from the document DE 102 32 530 A1. The selector interlock comprises a locking cylinder having a locking bolt aligned perpendicular to the gear shift shaft that is constantly subjected to pressure from lubricating oil of the manual transmission. In the case of high lubricating oil pressure, present during travel with the clutch engaged most of the time, the locking bolt presses against the spring force of a reset spring into a locking position in which axial displacement of the gear shift shaft into an outer shift gate allocated to the reverse gear is blocked in a form locking manner. In the case of low lubricating oil pressure, present when the vehicle is stopped and the clutch disengaged, the locking bolt is pressed by the reset spring into its rest position, and with that it is possible to select the outer shift gate and to engage the reverse gear.
The document, DE 199 08 147 A1, describes a shifting device of a manually shiftable transmission having a speed dependent selector interlock. This known selector interlock comprises a centrifugal force measurement mechanism that is preferably disposed at the output shaft which is in constant drive connection with the drive wheels of the motor vehicle. At high speeds, a locking bolt mechanically connected to the centrifugal force measurement mechanism is pushed into a locking position in which axial displacement of the gear shift shaft into one of the outer shift gates allocated to the reverse gear is blocked in a form locking manner. At low speed, in particular when the vehicle is stopped, the locking bolt is pushed back by a reset spring into its rest position, and with this the outer shift gate with the reverse gear is unblocked.
The selector interlocks of the shifting devices described above can, with a relatively small modification effort, also be used for the operation dependent blocking of an outer shift gate allocated to the highest forward gears. Using the selector interlocks known from the documents, DE 100 31 754 A1 and DE 31 41 271 C2, inadvertent selection of an outer shift gate is not reliably prevented due to the mode of operation of these selector interlocks that increase the actuating force. In addition, the known selector interlocks according to the documents DE 31 41 271 C2, DE 30 46 885 C2 and DE 199 08 147 A1 comprise an unfavorably high control effort that is associated with high production costs and high susceptibility to failure. The selector interlocks known from the documents DE 31 41 271 C2, DE 30 46 885 C2 and DE 102 32 530 A1 are furthermore judged to be particularly susceptible to failure due to their function that is based on pressure means.